DESCRIPTIVE DETAILS : CERRILLOS FIELD 649 



The conglomerate shown at the top of this section constitutes the base 

 of the Galisteo sandstone. In it were found pebbles and boulders up to 

 6 inches or more in diameter, consisting of quartz, chert, sandstone, 

 limestone, petrified wood, coal, etcetera. This formation is exposed con- 

 tinuously from Omera northward to Galisteo Creek and westward to 

 Madrid. 



Below the Mesaverde the Mancos shale occurs in characteristic devel- 

 opment. Great numbers of fossils, especially cephalopods, occur in con- 

 cretions of limestone near the top of the formation. The species collected 

 here are named in the accompanying section. The thickness of the 

 Mancos was estimated to be about the same as that given for it in the 

 Eogers section, but no attempt was made to measure it. It dips gently 

 toward the west and occupies the broad valley on either side of the Santa 

 Fe Central Eailroad. At the eastern side of this valley, about 3 miles 

 east of the town of Galisteo, a few Benton fossils were collected. They 

 are Ostrea sp., Inoceramus fragilis H. & M., Prionotropis sp., and unde- 

 termined casts of pelecypods and gastropods (United States Geological 

 Survey locality number 7170). 



About 2 miles south of the locality where these fossils were collected 

 the Tres Hermanos sandstone was recognized, and between this sandstone 

 and the Dakota the shale which contains the Gastropod zone at the locali- 

 ties described farther west. Below the Mancos shale is a hard conglom- 

 eratic sandstone which, on the basis of lithologic character and strati- 

 graphic position, is referred to the Dakota, and under it are variegated 

 sandstone and shale that probably are Morrison. 



The rock formations above the Morrison in this eastern limb of the 

 syncline correspond closely with those in the western limb, but below the 

 Morrison there seems to be a difference. East of Omera a massive, cliif- 

 making sandstone, about 100 feet thick, pink to red in color, occurs below 

 the Morrison and lies unconformably on the deep red and purple sand- 

 stone and shale of the typical red bed formation of this region. This 

 sandstone has the appearance of the Exeter sandstone (81, page 45) of 

 eastern New Mexico and holds the same stratigraphic position. It was 

 not recognized in the western limb of the syncline in the Cerrillos field, 

 nor farther southwest in the Hagan and Tijeras fields, although it may 

 be represented west of the Eio Puerco by a red cliff-making sandstone 

 which occurs below the Morrison. Below this sandstone east of Omera 

 occur red rocks similar to the Manzano red beds that underlie the Morri- 

 son west of the Cerrillos field. 



The line of outcrop of the coal beds extends from Omera in a north- 

 westerly direction and seems to pass around the northern base of the 



